Apparatus for knurling printing rolls



y 9, 1957 c. L. WOODWORTH 2,798,387

APPARATUS FOR KNURLING PRINTING ROLLS Filed June 25, 1953 2 Sheets-Sheet1 1N VEN TOR.

BYM Q a ATTORNEY 0/5573? L. WOODWQRTH y 1957 c. wooDwoRTH 2,798,387

APPARATUS FOR KNURLING PRINTING ROLLS Filed June 25, 1955 2 Sheets-Sheet2 2 Y W h? I 34 4 INVENTOR. w My L WWW/w (59 BY am/imezfl ATTORNEYAPPARATUS FOR KNURLING PRINTING ROLLS Chester L. Woodworth, Longmeadow,Mass, assignor to Monsanto Chemical Company, St. Louis, Mo., acorporation of Delaware Application June 25., 1953,:Seriai No. 364,133

Claims. (Cl. 7813.1)

This invention relates to apparatus for knurling printing rolls. Moreparticularly, this invention relates to apparatus for knurling printingrolls to be used in the printing of plastic interlayers for safety glasslaminates.

Safety glass is ,formed from a plastic interlayer sandwiched betweenglass plates. ,It is widely used in the automobile industry to formWindshields that will not shatter under impact. In order to eliminatethe glare encountered in driving, it has become the practice to colorthe upper portion of such Windshields by dying the plastic interl-ayer.The dye is applied in amanner such that there is a substantially uniformgradation of color of gradually diminishing intensity from the moreheavily dyed upper portion of the interlayer to the midportion thereofwhere the dye is no longer applied. it is conventional practice .tomodify the gradation .adjacent to the line of demarcation between "thedyed and undyed portions of the interlayer in order to eliminate theoptical aberrationsthatoccur when a completely uniform gradationabruptly ceases. From this, it is seen that the dyeing of interlayers ofthis character presents a special problem and that the dye must beapplied with care .and precision if satisfactory results are to beobtained.

In accordance withconventional practice, an interlayer is colored bybeing progressively immersed in and withdrawn from-a solvent solution ofdye. It has been proposed to apply the dye to the interlayer -by means:of a printing process wherein a knurled printing roll-is'used to applythe dye. .In accordance with this procedure, distinctseparate hollows,,or knurls, are formed in the surface of a printing :iOll for thereception of the :dye. The dye .pick-up of .each individual knurl isdependent on the depth thereof. By providing ,a printing roll whereinthe depth of the individualknurls is progressively diminished ina;predeterrnined manner, it is possibleto prepare plastic interlayers:havinga uniform gradation of color by a printing process.

Reasonably satisfactory printing rolls can be prepared by mechanically'knurling a printing roll uniformly throughout its length :.so:that thedepth of knurl is constant and then manually grinding the roll with anabrasive in order to obtain :aroll that will print a desired gradationas shown in U. S. Patent 2,638,050 to W. H. King. However, this processis .costly and time consuming. Past attempts to knurl such printingrolls by exclusively mechanical means have not been entirely successfulin one respect or another.

Accordingly, an object of the present invention is the provision ofapparatus for accurately knurling aprinting roll which maybe used in theprinting of safety glass interlayers.

Another object is the provision of apparatus for accurately controllingthe depth of .knurl imparted to a printing roll.

The manner in whichothese and other objectsarenats taine'd will beapparent from the following detailed-description of a specificembodiment .of the .presentinvem tion, when read in conjunction with theaccompanying drawingsin which:

Figure 1 is a side elevation view partly in section illustratingschematically a preferred form of the invention, the electrical circuitfor the knurling assemblybeing diagrammatically illustrated;

Figure 2 is a fragmentary top plan View of the apparatus shown in Figurel;

Figure 3 is a top plan view to an enlarged scale of the Lknurlingassembly shown in Figures 1 and 2;

Figure 4 is a fragmentary side elevation view to an enlarged scale of aknurling assembly shownin Figure 2, taken along the lines 4-4 of Figure'2;

Figure 5 is a front view of one form of a variable resistance elementcomprising a part of the current regulator shown in Figure '1; and

Figure 6 is a front view of another form of a Variable resistanceelement comprising apart of the current regulator shown in Figure =1.

Turning now to the drawings and especially to Figures 1 and 2, there isschematically shown a conventional lathe including a suitable base ,12,a headstock 14 carrying a chuck jaw 16 and a tail stock 18 carrying adead center .20. A printing roll 22 is mounted between the chuck jaw 16and thedead center 20 forrotational movement about its longitudinalaxis. A power-driven lead screw 24 and a ,guide vrail 26 support ,acarriage 28 heneath the live center .16 and the dead Center .20 fortravel therebetween in response ,to rotation ,of the lead screw 24. Thelathe is connected with a suitable poWersour-ce (not shown) by anyconventional means, a drive pulley 30 interconnected with the powersource by means of a belt 32 being one satisfactory means "by which this;is accomplished. The chuck jaw 16 and lead screw 24 may be driven bythe same power source-or the lead screw-24 may be driven independentlyof the chuck jaw 16 by any suitable .means :(not shown). .Lathes of thischaracter have long been in .use and their-construction and manner ofoperation is well-known to those skilled ,in the art. Accordingly, in.the interest of s mplicity, .the lathe has been schematicallyillustrated, the construction of the lathe, ,per-se, .not constituting apart of the present invention.

A vibrator assembly 34 mounted on the carriage 28 .is used .toiknurl theprinting roll 22, -the vibrator assembly 34 being energized by asuitable electric current-that is preferably derived from a power sourceindependent of the power source for the lathe. Any suitable vibratorassembly 34 may be utilized to knurl the roll 22, it only beingnecessary to adopt a construction that .will not set ripen-undesirableresonance.

A preferred form of vibrator assembly '34 is shown in thedrawings, theconstruction being more apparent from an inspection of Figures 3 and 4.In accordance with the preferred construction, a generallyU-shapedchannel member formed of a non-magnetized material such as brass isfixed to the carriage 28 by any suitable means such as an upstandingcolumn '38 formedintegral-ly therewith. The channel memberis defined bya web 40 interconnecting a pair of spaced parallel flanges 42 and 44that face the roll 22. A suitable apparatus for energizing a stylus isfixed to the web 40 intermediate the flanges 42 and 44. Such apparatusmay be, for example, a conventional electromagnet comprising an ironcore 48 surrounded by a coil 50.

A yibrator plate 52 is fixed to the ends of the flanges 42 and .44 inproximity to the electromagnet by-any suitable meanssuch as bolts 54,rubber blocks 56 being interposed between t-hevibrator plate 52, theheads of the-bolts 54 .andtheends of the flanges 42 and.44 inordertoprevent the transmission of undesirable vibrations to the fixedto the side of the vibrator plate 52 facing the electromagnet in spacedalignment with the iron core 48. A stylus 60 having a base 62 is fixedto the other side of the vibrator plate 52, the base 62 being attachedto the vibrator plate 52 opposite the button 58.' The stylus 60 shouldbe of length such that the tip thereof is normally spaced from but isengageable with the surface of the roll 22. The tip of the stylus 60 ispreferably'of a pyramid shape in order to produce pyramid-shaped knurlsin the surface of the roll 22.

The coil 50 is energized by a pulsating electric current generates apulsating magnetic field, e. g., an alternating current or a pulsatingdirect current. The electric current should be derived from a powersource capable of delivering a current of substantially uniformintensity and, in addition, the frequency of the pulsating current fshould be substantially uniform throughout knurling operations.

- When the coil 50 is energized by means of an alternating current, theiron core 48 is magnetized during each alternate half cycle in a degreeproportional to the current flowing through the coil 50; the magneticforce being released on each passage of the alternate current throughzero voltage. As a result, the button 58 will be drawn towards the ironcore 48 while it is magnetized and, when the magnetic force is released,the button 58 ing through the coil 50. During oscillation, thepyramidshaped tip of the stylus 60 will repeatedly strike the roll 22and produce knurls or depressions in the surface thereof, the depth ofthe knurl likewise being proportional to the intensity of the electriccurrent flowing through the coil 50. When a pulsating direct current isused, the 1 stylus 60 is vibrated in the same manner. The iron core 48is magnetized by each pulse of current passing through the coil 50 andthe magnetic force is released between pulses. As a result, theamplitude of vibration of the stylus 60 and the depth of knurl producedin the surface of the roll 22 will be proportional to the intensity ofthe pulsating direct current.

It is preferable to use an alternating current such as an alternatingcurrent derived from an independent power source 64 (schematicallyshown) that is capable of delivering a current of uniform intensity andfrequency. The coil is electrically connected with the power source 64by means of a circuit comprising a lead wire 66, a return wire 68, avoltage regulator 70 and, preferably, a suitable switch 72, the variouselements being connected in series. If a pulsating direct current is tobe used, the

coil 50 should be connected in the indicated manner with intensity overa comparatively wide range if the desired gradation of depth of knurl isto be obtained.

When the coil 50 is energized by an alternating current, thecurrentregulator to be used in accordance with the present inventionshould be one of two general constructions. Preferably, the constructionshould be such that the phase relationship of current to voltage 18 notchanged during knurling operations. However, if desired, a currentregulator that will continuously and umforrnly modify the phaserelationship of current to voltage as the intensity of current iscontinuously modified may be used. Current regulators of these twogeneral constructions are inherently operable to continuously anduniformly modify current intensity. A current regulator that modifiesthe phase relationship of current to voltage at a variable rate willgenerally be incapable of accurately controlling current intensity overthe entire range that must be used if satisfactory printing'rolls are tobe prepared. a

In accordance with the illustrated form of the invention, currentintensity is modified through the use of a voltage regulator 70 that iscontrolled by lateral movement of the carriage 28 relative to a roll 22being knurled, the illustrated regulator being operable to controlcurrent intensity when either a direct or alternating current is used.It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of elementscomprising the illustrated voltage regulator 70 since the invention iscapable of other embodiments and of being carried out in difierent ways.

As is more clearly shown in Figure l of the drawings, a preferredembodiment of the voltage regulator 70 comprises a container 74partially filled with a liquid electrolyte 76 and a pair of spacedelectrically conductive plates 78 and 80 immersed in the electrolyte 76.The plate 78 is fixedly mounted on the container 74 so that the immersedarea thereof will remain constant throughout knurling operations and theplate 80 is movably suspended in the electrolyte 76 so that the immersedarea may be varied.

Voltage regulators of this general construction will accurately register1 ohm changes in resistance over a 200 ohm range and will not modify thephase relationship of current to voltage when an alternating current isused. The electrical conductivity of the voltage regulator is determinedby plate size, plate spacing, the chemical composition and concentrationof the electrolyte and the temperature at which the electrolyte ismaintained during knurling operations. As a result, electricalconductivity can be controlled with precision in order to provide anydesired degree of conductivity. The plates 78 and 80 may be formed fromany suitable electrically conductive metal such as aluminum. Anysuitable liquid that is capable of conducting an electric current may beused as the electrolyte 76. A suitable electrolyte may comprise, forexample, an aqueous solution of 0.6 gram K of disodium phosphate perliter of distilled water. During knurling operations, the portion of theelectrolyte intermediate the plates 78 and 80 will be heated due to thetransmission of current between the plates. Since the temperature of theelectrolyte affects conductivity, it is preferable to mount a suitableagitator 82 intermediate the plates 78 and 80 to prevent localizedoverheating. The overall temperature of the electrolyte 76 is preferablymaintained constant throughout knurling operations by any suitable meanssuch as a cooling coil 84 connected to a suitable thermostaticallycontrolled cooler (not shown). It is preferable to provide a cover 86having suitable openings for the admission of the plates 78 and 80, theagitator 82 and the coil 84 in order to prevent contamination of theelectrolyte 76.

The voltage regulator 70 is placed adjacent the base 12 of the lathe andinterconnected with the stylus assembly 34 in a maner such that movementof the stylus 60 longitudinally of the roll 22 will cause the plate 80to be progressively withdrawn from the electrolyte. A suitableinterconnection comprises a cord 88 passing about a suitable pulley 90,one end of the cord 88 being fixed to the stylus carriage 28 and theother end being fixed to the plate 80. While this is a very simple anddiceztive arrangement, it will the apparent to, those skilled-in the artthat the interconnectionbetween the stylus 60 and the ,plate --80'may beaccomplished in many different ways through theuse 'of a iwidetvarietyof apparams.

OPERATIGN .A printing roll to be .knurled, .for example, a roll 22formed from mild steel, 'is mounted-on the-lathe between the chuck jaw16 and the dead center 20, care being taken to besure that theicentersare true. The stylus assembly 34 is positioned adjacent the dead center20 at one end of the roll 22 with the tip of the stylus spaced from thesurface -of-the roll "22. The current regulator 70 is then set to--provide an initial maximum depth of knurl. This is accomplished byimmersing the plate 80 in the electrolyte 76-to*a predetermined maximumextent, the spacing betweenthe plates '78 and 80, the immersed area of-the-plate 78 and the 'composition'and temperature of theelectrolyte'76beingtaken into account.

When the 'proper'adjustments have been made, ,power. is delivered to thelathe '10 "byrneans of a drive pulley in order to rotate-the roll '22about its:longitudinal .axis and also to rotate the lead screw24. As thelead screw 24 rotates, the carriage1'28 :andthe/vibrator assembly 34mounted thereon are movedlengthwise of the troll-22 towards the chuckjaw 16. Simultaneously, the switch 72 is closed in order to energize thecoil by an alternating current delivered from the power source 64.Alternate magnetization and demagnetization of the iron core 48 willcause the vibrator plate 52 and the stylus to oscillate whereby thestylus 60 will repeatedly strike the rotating roll 22 and produce knurlson the surface thereof. Since the carriage 28 is continuously movingrelative to the length of the continuously rotating printing roll 22,oscillation of the stylus 60 will produce a spiral pattern of separateknurls in the surface of the roll 22. The spacing between the individualknurls in the spiral will be determined by the rate at which the roll 22rotates and the rate of oscillation of the stylus 60. The spacingbetween laps of the spiral will be determined by the rate at which thecarriage 28 moves relative to the length of the roll 22. Any desiredknurl spacing can be obtained by suitably regulating the rate at whichthe roll 22 is rotated, the rate at which the carriage 28 is movedrelative to the roll 22, and the rate at which the stylus 60 oscillates.

As the carriage 28 moves progressively towards the chuck jaw 16 due tothe rotation of the lead screw 24, the cord 88 will progressively raisethe plate 80 of the voltage regulator 70. This Will cause the resistanceof the voltage regulator 70 to progressively increase at a uniform rateand thereby cause a correspondingly diminution of depth of knurl in thesurface of the roll 22.

When the plate 80 has straight parallel sides as shown in Figure 5, asubstantially uniform gradation of depth of knurl will be obtained. Ifthe plate 80 is tapered adjacent the bottom edge as shown in Figure 6,the gradation will be initially uniform but will be modified adjacentthe lightly knurled end of the roll 22 in order to prevent an abrupttermination of gradation. Other patterns may be formed in the surface ofthe roll 22 by using a plate 80 having any desired shape.

The following specific example illustrates the manner in which aprinting roll having a uniform depth of knurl is prepared When using theillustrated device which constitutes a preferred embodiment of theinvention.

Example I A printing roll 22 having a diameter of 2.90 inch is mountedbetween the chuck jaw 16 and the dead center 20 of a suitable lathe, thecenters having a trueness of plus or minus 0.0005 inch. The chuck jaw isset to rotate the roll 22 at a rate of 6.7 R. P. M. in order to providea cell spacing of 120 knurls per inch about the circumference of theroll 22 when using an alternating current having afrequency of 60 cycles,per second. The-carriage .28 is positioned adjacent the dead center :20and set to moveilengthwise ofthe roll 22 ataspeed to give 128 laps ofknurls ,per inch .of roll 22. A-pyramid-tipped carbide .steel stylus Mainchin diameter and inch long mounted .on the ,plate .52 is .used forthe actual lending. The plate .52 .is :spaced about A inch from the ironcore 48 .of theelectromagnet. The stylus 60.is mounted with the tipithereof spaced .0.0 1-2.inch from the surface of the troll '22,..thestylus 60 beinghorizontaland-Ms inch below the horizontal axis of theroll 22. By mounting .the stylus .60.slightly .below the center-of theroll 22 'in this fashion, the burrs orsmall-projections .of metalformed-on the surface of..the ?roll.22 by the gouging action .of thestylus .60are equalized on :opposite .sides of .the individual .knurlsfor v.easy removal with an emery cloth or other siutable abrasive.

With respect .to the voltage regulator 70, a solution of 2.5 ,grams ofdisodium phosphate :in -4 liters of 'water (the electrolyte 76) -.isplaced in a suitable container 74 and .two rectangular chromium vplatedsteel sheets '4 inches wide and .6 inches long are fully immersedtherein. The .plate :18 is-fixed .to the container 74 and the plate '80is suspended in the electrolyte 76 by a suitable .cord 88 thatfiXGdttQthfi carriage 28 and passes about a pulley 90 positioned above:the platez80. "The spacing between the plates is adjusted to give aninitial current of 1.4 amperes at an electrolyte temperature of about 40C.; the electrolyte 76 being maintained at about this tem peratureduring knurling operations.

When these adjustments have been made, the lathe is set in operation anda 60-cycle alternating current is delivered to the coil 50 of theelectromagnet. The ini tial (maximum) depth of knurl will be about 0.003inch. As the carriage 28 moves lengthwise of the roll 22, the plate willbe progressively withdrawn from the electrolyte 76 thus progressivelyincreasing the resistance of the current regulator 70. Since resistanceis increased at a constant rate, each individual knurl formed on thesurface of the roll 22 will have a depth slightly less than the depth ofthe next preceeding knurl. As a result, a knurled printing roll having auniform gradation of depth of knurl is obtained. It is preferable to rubthe surface of the roll 22 with an emery cloth or other suitableabrasive after knurling operations are complete in order to remove anyburrs that may be present on the surface thereof. A printing rollprepared in the above manner can be used to satisfactorily print aplastic interlayer for use in the preparation of glare-resistant safetyglass.

Having thus described my invention, what I claim is:

1. In a device for knurling a printing roll being rotated about itslongitudinal axis at a constant rate by means of a vibratable stylusperiodically engageable with the roll to produce indentations in thesurface thereof, the improvement which comprises support means formoving the stylus lengthwise of the rotating roll from adjacent one endthereof at a constant rate, an electromagnet responsive to analternating electric current carried by said support means for w'bratingsaid stylus at an amplitude of vibration proportional to the intensityof the electric current, an electric circuit connected to saidelectromagnet for delivering an alternating current thereto, saidcircuit including a control member, said control member comprising acontainer, a liquid electrolyte in said container, means for maintainingthe electrolyte at a substantially constant temperature, a firstelectro-conductive plate fixed to said container and immersed in saidelectrolyte, a second electro-conductive plate and means carried by saidsupport means for suspending said second electro-conductive plate insaid electrolyte and for unidirectionally varying the immersed areathereof at a rate determined by the rate of movement of the stylusrelative to the length of the roll.

2. Apparatus as in claim 1 wherein the second electroconductive plate isrectangular in shape.

3. Apparatus as in claim lwherein the second electroconductive platecomprises a first portion of uniform 'width and a second portion ofnon-uniform width.

4. In a device in which a printing roll beingrotated about itslongitudinal axis at a constant rate is knurled by means of a vibratablestylus periodically engageable with electrical means for vibrating thestylus at an amplitude of vibration proportional to the intensity of anelectrical current fiowing therethrough, said electrical means includinga control element cooperating with the support means to decrease theintensity of the electrical current continuously in direct response tothe movement of the support means.

improvement which comprises support means for moving the syluslengthwise of the rotating roll from adjacent one end thereof at aconstant rate, vibratory means carried by the support means forvibrating the stylus in response to a pulsating magnetic field generatedby an electric cu'rrent at an amplitude of vibration proportional to theintensity of the current and electrical means for delivering an'eleetriccurrent having a pulsating magnetic field to said vibratory means, saidelectrical means including a control element cooperating with thesupport means to decrease the intensity of the electrical currentcontinuously in direct response to the movement of the support means.

References Cited in the file of this patent UNITED STATES PATENTS515,241 Lyon Feb. 20, 1894 767,833 Phillips Aug. 16, 1904 960,626Crossland June 7, 1910 1,008,701 'Crump Nov. 14, 1911 1,626,014 Smith etal. Apr. 26, 1927 1,695,617 Teissere et a1. Dec. 18, 1928 1,772,650Weyandt Aug. 12, 1930 1,918,456 Dodge July 18, 1933 2,588,006 HufnagelMar. 4, 1952 2,598,253 Greenberg May 27, 1952 2,638,500 Ernst May 12,1953 FOREIGN PATENTS 406,163 Great Britain Feb. 14, 1933

